1. Field of the Invention
The present invention relates to carriers and facility interfaces, and more particularly to semiconductor wafer carriers and facility interfaces.
2. Description of the Related Art
With advances in electronic products, semiconductor technology has been applied widely in manufacturing memories, central processing units (CPUs), liquid crystal displays (LCDs), light emitting diodes (LEDs), laser diodes and other devices or chip sets. In order to achieve high-integration and high-speed requirements, dimensions of semiconductor integrated circuits have been reduced and various materials, such as copper and ultra low-k dielectrics, have been proposed along with techniques for overcoming manufacturing obstacles associated with these materials and requirements.
FIG. 1 is a schematic drawing showing a traditional via hole structure. A copper layer 110 is formed over a substrate 100. An ultra low-k dielectric layer 120 is formed over the copper layer 110. A via hole 130 is formed within the ultra low-k dielectric layer 120 to expose the top surface of the copper layer 110. If the copper layer 110 is exposed to air, the top surface of the copper layer 110 reacts with oxygen in air, forming a copper oxide layer 140 due to oxidation. The copper oxide layer 140 can adversely affect the electrical connection between the top surface of the copper layer 110 and a conductive via plug filled into the via hole 130. In addition, the ultra low-k dielectric layer 120 absorbs moisture when exposed to air. Accordingly, great care should be taken to avoid exposure to air during critical process steps, such as via opening, formation of copper seed layers, copper chemical mechanical polish (CMP) and formation of the ultra low-k dielectric material.
Traditionally, after a critical process step, the substrate 100 is removed from the process chamber that performs the critical process step and temporarily stored in a cassette or front opening unified pod (FOUP) until subsequent processing. When the door of the cassette or FOUP is removed to allow placement of the substrate 100 in the cassette or FOUP, air from the surrounding environment including oxygen flows into the cassette or FOUP. After the door is closed, the air is sealed within the cassette or FOUP with the substrate 100. As described above, oxygen tends to react with the copper layer 110 formed over the substrate 100 to form the copper oxide layer 140.
In order to address this problem, a “Q-time” is required after a critical process step is performed in the semiconductor manufacturing process. The next substrate process must be performed within a set predetermined time period or Q-time, such as from 2 to 4 hours. If a subsequent process, such as formation of a barrier layer, does not occur within the time period, a cleaning process is required to remove any copper oxide layer 140 formed over the copper layer 110.
Due to high integration of semiconductor devices over substrate 100, a semiconductor process usually has a plurality of the critical steps each with an associated Q-time designed to protect the substrate. These Q-time requirements complicate the manufacturing processes. In addition, if a Q-time is missed, additional steps such as cleaning steps increase process time and complexity.
By way of background, U.S. Pat. No. 6,506,009 provides a description of a prior art cassette stocker, the entirety of which is hereby incorporated by reference herein. U.S. Patent Publication No. 2003/0070960 provides a description of a prior art wafer cassette for storing and transporting wafers, the entirety of which is hereby incorporated by reference herein. Neither of these references provide a means for limiting formation of oxidation on or otherwise protecting surfaces of substrates when substrates are stored within or transferred to cassettes or FOUPs.
From the foregoing, improved cassettes or carriers and facility interfaces therefor are desired.